Computer Repair - Viruses 101

Computers 101 - Viruses

Q:
What is the difference between a Virus, Trojan, and Worm?

A:
Basically, they all fall under the generally category of "viruses". However, there are a few distinctions.

Virus - Technically, a virus infects another file (attaches or inserts itself into it). They usually infect program files or MS Office documents. From there, it can replicate, do damage, etc. Unlike a worm, these do not function as a stand alone (except possibly to infect a given file).

Worm - This is almost identical to a "true virus", except that it lives on its own and generally doesn't infect other files (although it can replace them). Usually, these copy themselves using e-mail, networks, disks, etc. Again, these are very close to a true virus, and can do the same kind of damage.

Trojan Horse - This type of program doesn't copy itself but does do damage to your computer. These types of programs rely on people to pass them around and to run them. They do not e-mail themselves. The idea is to make the program look like it's something harmless, like a screen saver or joke, so it gets sent around.

That's the crash course on virus types. Bottom line, you don't want any of the little nastys on your computer!
 

Tip of the Day

Although e-mail viruses are by far the most common, you can still get infected in any number of other ways. In this last section of our virus guide, we'll look at keeping you safe from as many virus sources as possible.

Unknown download sites - Be careful when downloading software from the net, especially from a virtual shareware library. A virtual shareware library is a site that has software listings on it, but they don't keep the software on their server. Just hover your mouse pointer over the download link and look at the bottom of your browser. If the URL shown is not the same as the site's it's a virtual shareware library. Most shareware sites are.

This isn't to say that you're going to get a virus by downloading software from them. In fact, I've never had a problem (and I download tons of software).

What I normally do is try to go to the software's web page. If it seems to be a trustworthy company, I download. Then I double-check the file with my anti-virus software.

Floppy Disks - Passing around floppy disks use to be the number one way of getting a virus, but it isn't as common as it used to be. In general, just be careful about running programs on floppy disks, especially those from questionable sources.

Another thing to be careful of is floppy boot sector viruses. If you have an infected floppy with this type of virus on it, you'll be infected if you forget to take it out of your drive when you re-boot your computer. To avoid problems, just don't leave floppy disks in your drive.

Of course, it doesn't hurt to scan your floppy with your AV software either.

Macro Viruses - I had mentioned these back in section two. Be careful with MS office documents that come from questionable sources. They can contain what's called a macro virus. These can delete files, alter program menus, and more.

Unfortunately, these are relatively easy to write, so they are among the most widespread variety of viruses. Be extremely careful when opening unknown MS office files, especially Word documents. Probably a good idea to save these files to disk then check them with your anti-virus software before opening them.

Well, that's about it. I know we could easily fill a book discussing viruses, but I'm just trying to pass along the basics.

Just remember, keep your anti-virus software up to date and don't run / open any files you don't trust 110%.